Solinco Hyper-G "Heaven Strings" Poly (polyester) 16/17/18/19/20 Gauge Tennis Racquet Sets are the best choice for the professional or advanced player seeking greater control, spin and durability in their choice of strings. They are often used as one half of a hybrid setup, usually with a slightly softer string like a multifilament in order to increase spin and durability without sacrificing too much playability. Length: 40ft / 12m; Composition: Co-polyester monofilament; Durability: 8 out of 10; Spin: 9 of 10; Playability: 7 out of 10; Power: 6 out of 10; Comfort: 6 out of 10.